Am 23.03.2014 18:38, schrieb Sean Kelly:
On Saturday, 22 March 2014 at 14:04:01 UTC, Daniel Davidson wrote:
For example, I could see technical reasons why in certain non-quant
areas like XML parsing where D can be faster than C++.
(http://dotnot.org/blog/archives/2008/03/12/why-is-dtango-so-fast-at-parsing-xml/)
But then, with a large amount of time and unlimited funding the
techniques could probably be duplicated in C++.
Try no funding and a trivial amount of time. The JSON parser I wrote
for work in C performs zero allocations and unescaping is performed on
demand. D arguably makes this easier by building slicing into the
language, but not decoding or copying is a design decision, not a
language artifact (at least in the case of C/C++ where aliasing data is
allowed). The take-away from that Tango article is that the performance
hit for parsing is aggressively decoding data the user may not care
about or may not want decoded in the first place. This just happens to
be the approach that basically every XML parser on the planet uses for
some ridiculous reason.
At least on Java world it is not quite true.
If you use XML parsers that return a DOM or SAX, yes quite true.
But as far as I can tell, XML streaming parsers (StAX) only parse on demand.
Unless I am missing something.
--
Paulo
